Quite a simple question, is going 'out of bounds' (i.e., avoiding the first set of sliding blocks in Spring Yard Zone Act 1) classified as a glitch, or just a good shortcut?

Not sure what you mean. You can go over and under things but not through them. If the runners avoid doing something, it probably is a glitch and vice versa

In the opening section of Spring Yard Zone, you can clear the wall directing you to go down the moving blocks, by collecting the sprint shoes monitor at the beginning then using the red spring to get enough height to go off the top of the screen and cut out a section of the level. You do this yourself in your record - - just wanted clarification as to whether this is deemed a glitch or not, but as it's in the glitchless category I imagine the answer is no?

Perfectly fine. No one considers Sonic going off screen a glitch. You can do the same in SL2, SL3 and SY3 top route, at least.

OK cool, thanks for clarifying. I guess it's more of a programming oversight that you can get over that one and not other ones elsewhere (Star Light Zone springs to mind?)

Btw, you can do the same trick even on the mobile port.

Ha! That's brilliant.